<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
    <meta name="viewport" content="width=device-width">

    <title>Object-fit gallery</title>

    <link rel="stylesheet" href="style.css">
    <!--[if lt IE 9]>
      <script src="//html5shiv.googlecode.com/svn/trunk/html5.js"></script>
    <![endif]-->
  </head>

  <body>
    <div class="top-row">
      <img class="thumb">
      <img class="thumb">
      <img class="thumb">
      <img class="thumb">
    </div>
    <div class="second-row">
      <img class="thumb">
      <img class="thumb">
      <img class="thumb">
      <img class="thumb">
    </div>
    <div class="third-row">
      <img class="thumb">
      <img class="thumb">
      <img class="thumb">
      <img class="thumb">
    </div>
    <div class="bottom-row">
      <img class="thumb">
      <img class="thumb">
      <img class="thumb">
      <img class="thumb">
    </div>
    <img class="main">
  </body>
  <script src="main.js"></script>
</html>